1. Field of the Invention
The present invention relates to wireless networks that provide communication services between transmitters and transceivers. More particularly, the present invention relates to determining and using the spectrum availability based on the presence or absence of signals to reallocate power to enable services at the transceivers that do not interfere with existing transmissions.
2. Background of the Related Art
Wireless communications between varieties of devices is increasing. Frequency allocation of the radio spectrum, location of transmitters and devices and other factors impact the availability of a communication service, especially when trying to avoid interference with existing networks and transmitters. A service, for example, may be defined as transmit or receive actions using a wireless device. A telephone call, downloading files, text messaging, and the like are all examples of services that may be initiated if the spectrum is available.
Thus, instances may exist where one wishes to transmit at a certain power level within an available portion of the spectrum that is not being used within a certain geographical region. This portion, also referred to as a geographical spectrum hole, is sensed and discovered using algorithms and measurements. Thus, if a spectrum hole is determined, then a node, or transceiver, can transmit or receive communications in the unused portion of the spectrum.
In wireless networking, the radio spectrum is shared dynamically over time between primary networks and nodes. Certain nodes are referred to as next generation, or XG, nodes. Each node is equipped with the sensing and discovery algorithms to delimit the geographical regions with unused spectrum, or the spectrum holes. Spectrum sharing behaviors include protocols or schemes employed by a transceiver to select transmission channels and power levels to avoid causing significant interference to primary networks or existing and non-cooperative (NC) users. Depending on the scenario, different types of dynamic spectrum sharing behaviors may be used by the transceiver.
For example, single node behaviors use spectrum occupancy measurements made by a single transceiver to determine if a channel can be used by the transceiver without causing significant interference with existing networks. One such process is referred to as Listen-Before-Talk (LBT). LBT causes the transceiver to abandon a channel and move to a different one if a received measurement is above a threshold, which may be referred to as a positive reading. The LBT process on an XG node uses an algorithm that integrates power within a particular frequency band over a short-time interval, or listening period.
If the received measurement includes signal power below the detection threshold, then a negative reading is noted by the LBT process. A negative reading indicates that a spectrum hole may exist for the listened channel. Thus, the transceiver is able to transmit at a conservative power level for a short period of time, or a transmitting period. The spectrum hole of the LBT process implies a circular spectrum hole centered at the measurement location with a radius approximately equal to a distance percentile, or α, where α is less than 1%. The distance percentile, or α, can be determined in several ways known in the art, such as using a model, using simulations or through real testing measurements.
The LBT process, however, fails to keep track of the spectrum holes discovered with past measurements. The LBT process discards the measurements after they are analyzed. Thus, the spectrum hole remains constant and changes its location along the movement trajectory to the positions where the measurements are taken. Further, the spectrum availability determination is limited to the area of that spectrum hole. This area, depending on transmit power and other factors, may not be large or reliable enough to provide an appropriate listening period to determine the presence of a NC transmitter. In addition, interference may occur as the transceiver moves its location after the initial LBT determination is made.